1908] HARVEY—PRAIRIE-GRASS FORMATION 97 
slopes and is found inclusive in Poa sods. C. festucacea occurs 
likewise on lower slopes, but more abundantly and assumes the 
“bunch-habit” of growth. Both the carices perennate and propagate 
vegetatively by rhizomes. They contribute little if any to the floral 
tone of the aspect. 
Florally associated with the carices, as just noted, are Vicia linearis, 
Senecio plattensis, and Pentstemon gracilis, to which are soon added 
Lappula texana and Plantago Purshii. Vicia occurs rarely, is con- 
fined to lower slopes, and exerts no tone effect; it isa perennial form 
and is pollinated by bees. Senecio, also of rare occurrence, seems to 
be confined to mesophytic portions of the formation. It is conspicu- 
Ous On account of its numerous yellow heads and ray flowers. But 
for its limited occurrence it might easily dominate the tone, and in 
the vicinity of Sioux City it was recorded as controlling the aspect. 
The achenes are provided with a copious pappus and a wide distribu- 
tion is assured. It is a perennial, and its scarcity seems to indicate 
that it is of decidedly mesophytic tendencies; it may be considered 
Prophetic in our area. Pentstemon gracilis, though rarely a com- 
Ponent in any plot, is an interesting form. It is confined to the 
mesophytic portions of the prairie and has been noted as abundant 
m Western Iowa. Its rarity in our area is explained as in the case of 
Senecio ; it is a perennial, and its smooth though numerous seeds are 
limited in their distribution. Lappula texana, the hairy stick-seed, 
's also a minor element, occurring mainly on lower slopes in sparse 
eee. It is much branched and its numerous small blue 
“rs exert but a restricted effect. It is an annual and very fertile, 
— esi nutlets whose margins are each bordered by a 
temas of bristles with recurved tips; distribution 1s entirely by 
The at It continues to bloom well into the estival aspect. 
HR, tele Plantain, P. Purshii, is a woolly annual whose indetermi- 
habit it some 20°", Of copious abundance and of gregarious 
is a becomes conspicuous at short distances. Its 
the early hagas up the spike, reaching the maximum in 
immobile seed at aspect and continuing well into July. Its highly 
account . Prevent other than a limited distribution, thus readily 
ng for its gregarious habit. 
© fourth week of the aspect, about the last week in'May, is 
